Patent Literature 1 has been well-known as a conventional circuit protector, which protects a circuit by detecting an abnormal current flowing in the circuit. This circuit protector comprises a semiconductor switching element connected between a power supply and a load and a protective circuit for outputting a control signal to the semiconductor switching element. The semiconductor switching element and the load are connected through a wire. A threshold current for damage prevention of the semiconductor switching element is set in the protective circuit. When an over current exceeding the above-mentioned threshold current is to flow between the semiconductor switching element and the load due to, for example, a short-circuit of the load, the protective circuit outputs an off-command signal to the semiconductor switching element and turns the same to the off-state. This can achieve the damage prevention of the semiconductor switching element.    [Patent literature 1]: Japanese Unexamined Patent Publication No. H04-334640
Such as aging degradation of the insulating coating of wires may probably cause a so-called layer “layer short circuit,” in which a current that is smaller than a threshold current for the damage prevention of the semiconductor switching element but is greater than the one at the time of normal energization, flows. In this case, according to the configuration of a conventional art, the current flowing in the wire is smaller than the threshold current, and the protective circuit does not therefore output an off-command signal to the semiconductor switching element. Therefore, a relatively large electrical current continuously flows in the wire, causing the heat generated from the core wire to remain in the wire, and thus may furthermore degrade the insulating coating of the wire.
In order to overcome the above problem, a temperature detection element connected with an abnormality determination circuit may be arranged in the wire, and when the temperature of the wire exceeded a threshold, the semiconductor switching element may be turned to the off-state.
However, in general, one temperature detection element is connected with the abnormality determination circuit through two conduction paths that are led out from the temperature detection element. The conduction paths twice as many as the temperature detection element are therefore separately required, and may cause a complicated configuration of the circuit protector on the whole.
The present invention has been completed based on the above circumstances, and its purpose is to provide a circuit protector having a simpler configuration.
The present invention relates to a circuit protector and an electric connection box comprising: a semiconductor switching element connected with a power supply, a conduction path connected with the semiconductor switching element and connecting the semiconductor switching element with a load, a semiconductor element having a PN junction and electrically connected with the conduction path to transfer heat, judgment means for judging whether a voltage drop value between input/output terminals of the semiconductor element is greater than a threshold or not, and control means for outputting an off-command signal to the semiconductor switching element when a judgment is made by the judgment means that the voltage drop value is smaller than the threshold.
In addition, the semiconductor element being connected with the conduction path to transfer heat means a state where heat is transferred from the conduction path to the semiconductor element so that the temperature of the conduction path and that of the semiconductor element become nearly the same, and, in short, the semiconductor element is connected with the conduction path.
An element for detecting temperatures and judgment means are generally connected each other through two leads led out from the element. According to the present invention, the semiconductor element is connected to both the conduction path and the judgment means. Accordingly, the conduction path can serve as one lead in the semiconductor element, and thus the configuration of the circuit protector can be simplified.
The present invention can simplify the configurations of the circuit protector and the electric connection box.